Central Sweden Trip - Uppsala, Mora, Rattvik,etc.- help with planning

I can't speak to your other locations, but we spent a long day in Uppsala in July. There were no dense crowds anywhere we went (University, museums, cathedral, etc) although cafes were moderately busy at lunch and fika time. Uppsala is not a large city by US standards. We had a nice walk in the historical area just outside of town at the ancient original church and prehistoric mounds. There were about 6 people walking around. I don't recall any bugs even though there was clearly bodies of water around.

That sounds lovely. We will be there this coming July, in Uppsala. Did you find a quiet place to stay there?

Sorry can't help you with lodging. We were with a friend who lives there. The area just outside of town I referred to is called Gamla Uppsala. I'd recommend you read at least the Wikipedia article on it before going because the RS description is a bit light and there is little information on-site. In addition to that area, the main cathedral in town, and the University museum ("Gustavianum") we also went to the home and garden of Carl Linnaeus ("father of modern botany") which is a pleasant and somewhat interesting tour if you are into plants and taxonomy. I'm not 100% sure since we did not linger in the center of Uppsala, but there is a small river that runs through town and I had the impression that there might be a path that follows it for some distance. Inquire locally. The countryside struck me as flat and pleasant, though not really amazing or overly picturesque.

A few comments on your selection:

Uppsala is a nice town, many people visit Uppsala as a day trip from Stockholm but there are more things to see and it's worth spending a few days here. Regarding lodging, Hörnan is a nice hotel located in a calm but still central part of the city centre.

Mora, very nice town. Don't miss the Zorn museum and his house.

Falun, also a nice town, a lot of older (19th century) wooden houses in part of the town. The mine though is probably the big tourist attraction.

Lövstabruk, nice small iron work village, but probably not nice enough to spend more than a few hours there. In the area I could add Öregrund, a nice coastal town. Like Sigtuna, but more beautiful in my opinion and less touristy.

Nora and Askersund, two more towns with old houses, but a bit out of the way and I'm not sure they'll add anything else to the trip.

Sala, famous for the silver mine, you can even spend a night in the mine. Also has a nice café close to the railway station.

Any reason for including Leksand? The town is famous for the knäckebröd bakery and a pretty good hockey team, as well as a slightly interesting church. Rättvik is also not a place I would spend too much time, but it is located in a very beautiful part of Sweden at lake Siljan with the longest wooden pier in Sweden (628 m). And when in the area, a visit to Nusnäs is a must.

Ängelsberg is also in a very beautiful spot but a very small village. If you're interested in industrial history you shouldn't miss Ängelsberg.